TimeSeries: Add support for negative Y and constant transform (#44774) (#45087)

* add negative y config

* Handle negative y and constant transform in Timeseries panel

* Typechecks

* Add migration from old graph panel

* Docs update

* Revert "Add migration from old graph panel"

This reverts commit 33b5a90b66.

* Revert VizLegendItem changes

* Automatically separate positive and negative stacks within a group

* Update packages/grafana-ui/src/components/VizLegend/VizLegend.story.tsx

* Remove SeriesLabel component

* Update docs/sources/visualizations/time-series/_index.md

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

* Update docs/sources/visualizations/time-series/_index.md

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

* Leftover reverts

* Don't crate bands (for now0 for negative -y stack

* Add docs note about transform being only available as an override

* Fill negative bands in reversed direction

Co-authored-by: Ryan McKinley <ryantxu@gmail.com>
Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>
(cherry picked from commit ffea53f2f6)

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

docs/sources/visualizations/time-series/_index.md

@@ -35,6 +35,15 @@ Use these options to choose how to display your time series data.
 - [Graph stacked time series]({{< relref "./graph-time-series-stacking.md" >}})
 - [Graph and color schemes]({{< relref "./graph-color-scheme.md" >}})
 
+### Transform
+
+Use this option to transform the series values without affecting the values shown in the tooltip, context menu, and legend.
+
+- **Negative Y transform -** Flip the results to negative values on the Y axis.
+- **Constant -** Show first value as a constant line.
+
+> **Note:** Transform option is only available as an override.
+
 ## Axis
 
 For more information about adjusting your time series axes, refer to [Change axis display]({{< relref "change-axis-display.md" >}}).